Question

a 1.00 L solution of calcium hydroxide has a pOH of 1.80. Calculate the mass of calcium hydroxide (Ca(OH)2) required to make this solution. **Hint use concentration of ions to solve this question

Answer 1

$$Ca(OH)_2 ↔ Ca^{2+} + 2OH^-$$

We take calcium hydroxide as a strong electrolyte. Then:

$$[OH^-] = 10^{-pOH} = 10^{-1.80} = 0.0158 M$$

$$c(Ca(OH)_2) = [OH^-] = 0.0158 M$$

$$n(Ca(OH)_2) = cV = 0.0158 mol$$

$$m(Ca(OH)_2) = nM = 0.0158 mol* 74.093 g/mol = 1.1707 g$$

Answer: 1.1707 g